Deconstructing the
MoviePlayer app to see how the Media Player Framework ticks.
MoviePlayer has 4 classes:
MoviePlayerAppDelegateMyImageViewMyOverlayViewMyViewController
A new IPhone application automatically creates 2 classes, with project name
MPC,
MPCAppDelegate and
MPCViewController. Therefore,
MyImageView and
MyOverlayView are additions while
MyViewController has been renamed.
MoviePlayerAppDelegate
Interface
There are 2 different ways of including a file/class:
#import "MyViewController.h"@class MyViewController;
The interface lists 3 instance variables of type
NSInteger aside from the default
UIWindow and
ViewController:
backgroundColorcontrolModescalingMode
The
@property declares the accessor methods for the 5 variables. It has attributes which modify the accessors.
Example:
@property (nonatomic, retain) UIWindow *window;nonatomic means the accessor returns the value directly, the default is to lock, get value, unlock which is meant for multithreaded environments.
assign,
retain or
copy must be explicitly set if garbage collection is not used.
assign is the default and means the setter uses a simple assignment.
retain keeps the object variable in-memory and cannot be deallocated without your permission.
copy means that a copy of the object should be used for assignment and the previous one is sent a release message.
3 instance methods:
-(void)setUserSettingsDefaults;-(void)applicationDidFinishLaunching:(UIApplication *)application;-(void)dealloc;
Implementation
3 NSString keys:
kScalingModeKey = @"scalingMode"kControlModeKey = @"controlMode"kBackgroundColorKey = @"backgroundColor"
@synthesize generates the accessors according to the attributes listed. If implemented manually, the code must follow what has been specified in the
@property.
@synthesize will only generate accessors that don't exist so if a variable has a setter already, then only a getter will be generated.
-(void)setUserSettingsDefaultsSets up a test calling
NSUserDefaults to see if there's a match. Passing will set the
scalingMode,
controlMode and
backgroundColor variables. Failing will create the values based on the settings bundle info and then set the variables:
- Get the path to the main bundle of the project.
- Append
Settings.bundle to the path using stringByAppendingPathComponent, which takes care of adding separators. - Append
Root.plist to the path, same as before. - Create a dictionary using
dictionaryWithContentsOfFile, giving the path to Root.plist. - Create the
prefSpecifierArray array from the dictionary using the key, PreferenceSpecifiers, which is a tag in Root.plist.Root.plist is an XML file with dict, array and key tags. May be an easy way to read XML.
- Declare 3
NSNumber variables and a dictionary, prefItem. - Loop
prefSpecifierArray with the current value going into prefItem. - Set
keyValueStr with the dictionary using the key, 'Key'. - Set
defaultValue with the dictionary using the key, 'DefaultValue'. - Check if
keyValueStr is equal to any NSStrings specified above. - Set the numbers with
defaultValue if any is correct.
- Create a dictionary containing the default values and their keys.
- Register the dictionary with
NSUserDefaults using registerDefaults. - Updates and writes to the persistent domains using
synchronize.
-(void)applicationDidFinishLaunching:(UIApplication *)applicationAdd the
ViewController's view as a subview of the
UIWindow. Call self with
setUserSettingsDefaults to get the default movie player settings. Lastly, call the
ViewController with
initMoviePlayer to create a movie player object.
-(void)deallocRelease the
UIWindow and the
ViewController. Call the super's
dealloc method.
